Froth flotation method



United States Patent Ofi ice 3,1 6 7,2 1% Patented Oct. 1 5, l 9633,107,214 FROTH FLGTATIGN R/ETHGD .iarnes B. Duke, Metuchen, N.5.,assignor to Minerals 8; Chemicals Philipp Corporation, Menlo Park, N.J.,a corporation of Maryland No Drawing. Filed Dec. 16, 1966, Ser. No.76,694 6 Claims. (Cl. 209-166) The subject invention has to do with anovel method for recovering certain collector coated solid particleswhich are used as an auxiliary reagent in conditioning discolored kaolinclay for froth flotation to beneficiate the clay, in accordance with theprocedure described in a copending patent application, Serial No.779,061, filed December 9, 1958, now US. 2,990,958, of which I am acoinventor. This application is a continuation-in-part of theaforementioned application. In accordance with the method disclosed andclaimed in said application, the grade and recovery of beneficiatedkaolin clay obtainable by froth flotation is improved by using, asconditioning reagents for a dispersed aqueous pulp of the clay, thecombination of a negative-ion (fatty acid) collector reagent selectiveto colored impurities in the clay and certain finely divided oiledparticles (hereafter referred to as carrier particles) which arefloatable in the reagentized pulp. The latter report in the frothproduct together with colored impurities originally in the clay(principally anatasea colored form of TiO and in so doing promote orenhance the flotation of the latter. The machine discharge product is aclay of enhanced brightness and reduced titania content. The method isapplicable to the beneficiation of sedimentary whole kaolin clay as wellas fine fractions or coarse fractions thereof. However, the optimumbenefits are realized in the treatment of whole clay or fine fractionsthereof for the reason that conventional froth flotation treatment isnot very effective (and in some instances is completely ineffective) inbeneficiating slimed ores such as whole clay or line fractions of clay.

It is obvious that the overall economics of the froth flotation processabove described could be improved by recovering the reagentized carrierparticles from the colored impurities with which they are intimatelyassociated in the froth product for the purpose, for example, ofrecycling the auxiliary particles in the flotation machines. However, itis obvious that any economically feasible method for accomplishing theseparation of the carrier from the colored impurities must be so low incost that it would counteract the cost of utilizing fresh carrierparticles in each operation. Thus, the equipment and reagents utilizedto effect such separation must add little to the overall cost of theprocess.

The separation is fundamentally diflicult for the reason that both thereagentized carrier particles and color body materials are in finelydivided form and adhere tenaciously to each other in the froth product.Acidulation or alkalization of the composite froth has been found tohave little effect on breaking up the strong bonds holding the varioussolid particles together.

Accordingly, it is a principal object of the subject invention toprovide, in a process for the froth flotation of discolored kaolin tofloat colored impurities therefrom and entailing the use of solidparticles as one of the conditioning agents, a simple, economical methodfor separating the solid conditioning particles from the coloredimpurities with which they are intimately associated in the frothproduct.

A more particular object of my invention is the provision of a novelmethod for eifecting such separation by froth flotation.

Still another object of this invention is the provision subjectinvention,

of a method for the froth flotation of discolored kaolin clay usingsolid carrier particles as a conditioning reagent in Which the carrierparticles are recovered and reused in the process and, at the same time,the colored impurities originally in the clay, which are floated alongwith the carrier, are separated therefrom.

A specific object of this invention is the provision of a simple,economical method for the froth flotation of finely divided reagentizedmineral particles from fatty acid reagentized slimed colored impuritiesoriginally in clay.

Further objects and advantages will be readily apparent from adescription of my invention which fol lows.

Briefly stated, in accordance with the present invention, an admixedpulp of fatty acid rcagentized mineral particles and slimed finelydivided titaniferous matter (obtained by subjecting to froth flotationan alkali silicate dispersed pulp of discolored clay which has beenconditioned with fatty acid and collector coated mineral particles) isconditioned with phosphate, especially tetrasodium pyrophosphate, andwith a low boiling petroleum hydrocarbon of the type Widely used as apaint thinner or solvent. The conditioning is carried out by initiallyagitating the composite froth with phosphate and thereafterincorporating the hydrocarbon liquid and agitating the Whole. The pulpthus conditioned is subjected to froth flotation thereby producing afroth product which is a concentrate of the carrier particles, leavingin the underflow the colored impurities which were originally in theclay. The froth product, after washing and being further conditionedwith suitable collector reagent, may then be reused in conditioning anaqueous pulp of discolored kaolin clay and the conditioned pulpsubjected to froth flotation in accordance with the procedure describedin said copending applications. The machine discharge may be treated forrecovery of its titanium mineral values or it may be discarded.

While I do not Wish to be bound to any theory or explanation of how thecombination of the molecularly dehydrated phosphate and light petroleumhydrocarbon liquid contribute to eifect the desired flotation of thecarrier from the colored impurities in the clay, the following isbelieved to oifer a plausible explanation. The phosphate, which is anextremely powerful mineral dispersant, appears to physically separatethe clay impurities from the carrier particles to which they adheretenaciously in the froth product, even in the presence of a silicatedispersant. Other mineral dispersants such as, for example, the alkalisilicates are not operative in the flotation process of this invention,seemingly for the reason that they are not efiective, as is mymolecularly dehydrated phosphate, in reducing the strong interparticleforces that exist between the components of the composite froth. As forthe role of the light petroleum hydrocarbon reagent, it is believed thatthe carrier particles have a greater aflinity for the hydrocarboncollector reagent than do the colored impurities originally in the clay.Therefore, it appears that the hydrocarbon liquid selectively reoilssuch carrier particles, having but little effect in this manner on thecolor impurities, thereby permitting the effective flotation of thecarrier particles from the colored matter.

More specifically, the composite froth product that is treated by frothflotation in accordance with the subject invention is obtained asfollows. initially, raw discolored kaolin clay is dispersed in water inany convenient manner With sodium silicate dispersant. While it has beennoted that the phosphate dispersants are, preferred in the carriermineral recovery process of the they are notas effective as the alkali amolecularly dehydrated of 6% to 25%. In accordance with one form of theinvention, described in the copending applications, a pulp of carrierparticles is mixed with the dispersed clay pulp and the admixed pulp isconditioned with a higher fatty acid collector reagent such as, forexample, tall oil fatty acids, oleic acid, resin acids, sulfonates ofthese and like acids, such as sulfo-oleic acid, and soaps of theaforementioned acids, or combinations of such fatty acid reagents. Inaddition to the collector reagent, an alkaline material, typicallyammonium or sodium hydroxide, is added to the pulp to bring the pH to 8to 10. Preferably, an oil-soluble petroleum .sulfonate is added, as wellas a material selected from the group of ammonium sulfate, magnesiumsulfate and potassium sulfate.

If desired, the silicate dispersed clay pulp may be reagentized with theaforementioned reagents and a pulp of carrier particles separatelyreagentized with the fatty acid collector together with such auxiliaryreagents as will enhance the collector coating of the carrier pulp.These reagentized pulps are then admixed.

The carrier mineral may be any one which has a strong aflinity for fattyacid oiling reagents. While calcite is a preferred carrier because ofits low cost and eifectiveness in the process, a variety of othercarriers will be suitable since the function of the oil carrier inimproving flotation is apparently a physical one, not chemical, Asexamples of other carriers may be cited barytes, sulfur and fluorspar.

The carrier mineral is finely divided, preferably, substantially all ofthe particles are minus 100 mesh. Especially good results are obtainedwith carrier particles which are 200 mesh or finer.

The carrier mineral is usually used in amount of about to 200%, based onthe dry clay weight.

Preferably, subsequent to the reagentization of the feed and theauxiliary mineral particles, the pulp is diluted and subjected .toaeration (and usually mechanical agitation) in any suitable flotationmachine although, in some instances, it may be advantageous to addadditional reagents during the concentration step. As a result of theaeration, the colored impurities, collector coated, report in the frothin association with the reagentized particles of auxiliary mineral (andusually some clay, depending of course on the efiiciency of theflotation). The composite froth is separated from the trailings ormachine discharge product whioh comprises a beneficiated claycharacterized by an enhanced whiteness and brightness and a reducedtitania analysis. Normally the froth product is r'efloated a pluralityof times to recover clay values entrained therein. In this case thefinal froth product or a portion thereof is conditioned in accordancewith the method of the subject invention.

The rfroth product, obtained as described above, and comprising analkaline concentrate of fatty acid reagentized carrier particles andcolored impurities originally in clay (and usually some clay), isagitated with a molecularly dehydrated phosphate such as, for example,sodium hexametaphosphate, disodium dihydrogen pyrophosphate or sodiumtripolyphosphate. Especially preferred is tetrasodium pyrophosphate. Thequantity of dispersant I employ is critical and is within the range ofabout 2 to 5 pounds per ton of the original clay feed (dry clay basis).When the phosphate is employed in amount less than the minimumindicated, the flotation hereafter described is ineifective because thecolored impurities adhere to the concentrate of carrier particles andare not amenable to separation therefrom. On the other hand, when thedispersant is employed in excess of the maximum indicated, the processtends to lose its eifectiveness because carrier mineral particles aredepressed and thus they are not amenable to concentration from thecolored impurities. A short conditioning time of the order of 1 to 3minutes will suifice. The froth is then further conditioned, either inan agitated conditioner or in the flotation machine for about 5 minutes,with a light hydrocarbon liquid such as mineral spirits, gasoline, lightnaphtha (e.g., V.M. & P. naphtha). The hydrocarbon liquid is agitatedwith the pulp to eifect the desired contact with the solids. Goodresults have been obtained using about 5 to 15 pounds of hydrocarbonliquid per ton of the original clay feed. When the quantity ofhydrocarbon liquid is insufiicient, the froth product will be watery andpoor concentration of the carrier particles will result. On the otherhand, use of excessive hydrocarbon liquid impairsthe selectivity of theflotation. The conditioned pulp, usually after addition of dilutionwater to reduce the pulp solids to about 5% to 15%, is aerated therebyproducing a froth product which is substantially free from anatase andother coloring material associated with the anatase in the originalfroth product.

The froth product is then filtered, Washed with water, slurried withwater and recycled to the conditioning macnines preceding the primaryflotation machines handling dispersed disclored kaolin clay pulp.

The following example illustrates the successful adaptation of myprocess to the recovery of a calcite carrier from the anatase and othercoloring materials associated with the anatase in the froth and there-use of the recovered calcite in the froth flotation of discoloredkaolin clay.

The starting clay was a crude discolored sedimentary Georgia kaolin clayknown as Klondylre crude and analyzing 1.78% TiO and about 1% Fe OTwenty-five pounds (dry basis) of the crude kaolin clay was stirred withabout 100 pounds of deionized water until practically all of the claylump-s were disintegrated. The slurry was screened to remove all plus325 mesh material. The degritted clay had the following particle sizedistribution: 98% by weight, minus 15 microns, 92% minus 10 microns,minus 5 microns, 50% minus 1.5 microns, and 15% minus 0.5 micron. Allparticle sizes refer to equivalent spherical diameters, as determined bythe Casagrande water sedimentation method. The slip was pulped withwater to a concentration of about 10% clay solids and agitated for abouta minute with sodium silicate in the amount of 0.3% (based on the dryclay weight).

In a continuous pilot plant operation employing about 1064 pounds perhour of the crude kaolin clay (dry clay basis), 52 pounds per hour ofnatural calcite (No. 1 white) was continuously added to the silicatedispersed kaolin slip. The particle size of the calcite was 98% byweight minus 40 microns, 36% minus 10 microns, and 7 10% minus 3microns. The admixed pulp of crude clay and calcite was conditioned withabout 6 pounds of ammonium sulfate, 7 pounds of a 1:1 emulsified mixtureof crude tall oil fatty acid and a neutral, oil-soluble petroleumsulfonate (analyzing 41.0% calcium sulfonate complex and the balancesubstantially mineral oil) and sufficient ammonium hydroxide to maintaina pH of about 8.5 in the conditioned pulp. All reagents are reported onthe basis of pounds per ton of the dry clay. The percent solids in theconditioner was about 18% and the retention time was about 25 minutes.This conditioned pulp was continuously fed to a 5 cell No. 8 Denverflotation machine, with dilution water added to the second, third andfourth cells. A finished machine discharge product was taken from thefifth cell, which was a high brightness kaolin clay slip and amounted toabout 58%, weight basis, of the original kaolin clay. The froth productfrom this operation was refloated three times in additional machines,thus producing three additional beneficiated machine discharges whichwere combined with the first machine discharge product to yield aboutweight recovery of high brightness clay containing a very smallpercentage of TiO and other coloring impurities.

The final froth product, carrying a major weight pro enc'zgaia 5 portionof the original anatase and substantially all of the calcite carrier,was treated as follows. In the sump pump, tetrasodium pyrophosphate wasadded to the froth in the amount of about 4.5 pounds per ton oforiginal. dry clay feed. The froth was added to an agitating machine andagitated for about 2 minutes. Mineral spirits the amount of about 13pounds per ton of original dry clay feed was added to the froth productand conditioned for about 5 minutes. This material was then subjected tocontinuous froth flotation. The froth product from this operation was aclean white calcite, substantially free from anatase and other coloringmaterials associated with the calcite in the original froth. The machinedischarge product was a concentrate of the anatase and other coloringimpurities associated with about 10% of the original kaolin clay.

The calcite froth product was filtered and washed with water on acontinuous rotary filter. The calcite filter cake was slurried withwater to about 40% solids and continuously recycled to the conditioningstep preceding the primary flotation machine in the amount of about 250pounds per hour.

I claim:

1. In a process for the froth flotation of kaolin clay containing colorbody impurities which comprises forming a dispersed aqueous pulp ofkaolin clay using an alkali silicate as a dispersant for said clay,conditioning said pulp for froth flotation with a fatty acid collectorreagent selective to color body impurities in said clay and finelydivided insoluble mineral particles which are reagentized with a fattyacid collector reagent and are fioatable in said pulp, subjecting thethus conditioned aqueous pulp to froth flotation in an alkaline circuitthereby producing a froth product which is a concentrate of said colorbody impurities in intimate association with said collector coatedmineral particles and a machine discharge product which is a concentrateof clay of enhanced brightness, the improvement which comprisesconditioning the froth product in the form of an aqueous pulp thereofwith a molecularly dehydrated phosphate dispersant in an amount withinthe range of about 2 /2 to 5 pounds per ton of the original kaolin clayemployed in the process and with a light petroleum hydrocarbon liquid,subjecting the thus conditioned aqueous pulp to froth flotation therebyproducing a froth product which is a concentrate of said mineralparticles and a machine i3 discharge which is a concentrate of colorbody impurities originally in said clay.

2. The method of claim 1 in which said phosphate is tet-rasodiumpyrophosphate.

3. The method of claim liquid is mineral spirits.

4. The method of claim 1 in which the froth product obtained bysubjecting to froth flotation the conditioned aqueous pulp of collectorcoated nnneral particles and colored impurities is washed, reconditionedwith a fatty acid collector reagent and reused in conditioning anaqueous pulp of discolored kaolin clay for froth flotation.

5. in a process for the froth flotation of kaolin clay contain ng colorbody impurities which comprises form ing a dispersed aqueous pulp ofkaolin c ay using an alkali silicate as a dispersant for said clay,conditioning said pulp for froth flotation with a fatty acid collectorreagent selective to color body impurities in said clay and finelydivided insoluble mineral particles which are reagentized with a fattyacid collector reagent and are floatable in said pulp, subjecting thethus conditioned aqueous pulp to froth flotation in an alkaline circuitthereby producing a froth product which is a concentrate of said colorbody impurities in intimate association with said collector coatedmineral particles and a machine discharge product which is a concentrateof clay of enhanced brightness, the improvement which comprisesconditioning the froth product in the form of an aqueous pulp thereofwith tetrasodiurn pyrophosphate in amount within the range of about 2 /2to 5 pounds per ton of the original kaolin employed in the process andthereafter with a light petroleum hydrocarbon liquid, subjecting thethus conditioned aqueous pulp to froth flotation thereby producing afroth product which is a concentrate of said mineral particles and amachine discharge which is a concentrate of color body impuritiesoriginally in said clay.

6. The method of claim 5 wherein said finely divided insoluble mineralparticles are calcite particles.

1 in which said hydrocarbon References Cited in the file of this patentUNITED STATES PATENTS UNITED STATES PATENT OFFICE CERTIFICATE OFCORRECTION Patent No. 3, 107 ,214 October 15, 1963 James B Duke It ishereby certified that error appears in the above numbered patentrequiring correction and that the said Letters Patent should read ascorrected below.

Colomn 3, line 27, for "oil" read oiled line 47, for tra11ings" readtailings column 4, line 21, for "disc lored" read discolored Signed andsealed this 14th day of April 1964.

(SEAL) Attest: EDWARD J. BRENNER ERNEST W. SWIDER Attesting OfficerCommissioner of Patents

1. IN A PROCESS FOR THE FROTH FLOTATION OF KAOLIN CLAY CONTAINING COLORBODY IMPURITIES WHICH COMPRISES FORMING A DISPERSED AQUEOUS PULP OFKAOLIN CLAY USING AN ALKALI SILICATE AS A DISPERSANT FOR SAID CLAY,CONDITIONING SAID PULP FOR FROTH FLOTATION WITH A FATTY ACID COLLECTORREAGENT SELECTIVE TO COLOR BODY IMPURITIES IN SAID CLAY AND FINELYDIVIDED INSOLUBLE MINERAL PARTICLES WHICH ARE REAGENTIZED WITH A FATTYACID COLLECTOR REAGENT AND ARE FLOATABLE IN SAID PULP, SUBJECTING THETHUS CONDITIONED AQUEOUS PULP TO FROTH FLOTATION IN AN ALKALINE CIRCUITTHEREBY PRODUCING A FROTH PRODUCT WHICH IS A CONCENTRATE OF SAID COLORBODY IMPURITIES IN INTIMATE ASSOCIATION WITH SAID COLLECTOR COATEDMINERAL PARTICLES AND A MACHINE DISCHARGE PRODUCT WHICH IS A CONCENTRATEOF CLAY OF ENHANCED BRIGHTNESS, THE IMPROVEMENT WHICH COMPRISESCONDITIONING THE FROTH PRODUCT IN THE FORM OF AN AQUEOUS PULP THEREOFWITH A MOLECULARLY DEHYDRATED PHOSPHATE DISPENSANT IN AN AMOUNT WITHINTHE RANGE OF ABOUT 2 1/2 TO 5 POUNDS PER TON OF THE ORIGINAL KAOLIN CLAYEMPLOYED IN THE PROCESS AND WITH A LIGHT PETROLEUM HYDROCARBON LIQUID,SUBJECTING THE THUS CONDITIONED AQUEOUS PULP TO FROTH FLOTATION THEREBYPRODUCING A FROTH PRODUCT WHICH IS A CONCENTRATE OF SAID MINERALPARTICLES AND A MACHINE DISCHARGE WHICH IS A CONCENTRATE OF COLOR BODYIMPURITIES ORIGINALLY IN SAID CLAY.